Cationic starch composition and process for making same

ABSTRACT

Disclosed herein is a new cationic starch and cationic starch paste or slurry. The starch paste or slurry has a low cation equivalent value despite its high nitrogen content and also has a low solution viscosity despite its high molecular weight. The cationic starch and cationic starch paste or slurry is formed by substitution with a one or both of quaternary ammonium salt or a tertiary amino group, characterized in that its nitrogen content (X) due to the quaternary ammonium salt and/or tertiary amino group is related to its cation equivalent value (Y) as defined below: 
     
         Y&lt;0.70097X-0.07978 
    
     (in the case of natural terrestrial stem starch) 
     
         Y&lt;0.32936X-0.00495 
    
     (in the case of natural subterranean stem starch having ester-type substituents) 
     
         Y&lt;0.40942X+0.02211 
    
     (in the case of natural subterranean stem starch having no ester-type substituents)

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to cationic starch and a cationic starchpaste or slurry for papermaking which has a high nitrogen content andyet has a low cation equivalent value. The present invention relatesalso to a process for producing the same.

Major terms and abbreviations used in this specification are definedbelow.

(1) Cation equivalent value (meq): Expressed in terms of values measuredby the colloidal titration of starch paste solution with PVSK (potassiumpolyvinylsulfate).

(2) Viscosity: Expressed in terms of values measured on a 1 wt % sampleat 50° C. with a Brookfield viscometer, unless otherwise mentioned.

(3) Nitrogen content: Expressed in terms of percentage (%) valuesmeasured on a sample of cationic starch by the semimicro Kjeldahlmethod.

(4) DS value: Expressed in terms of an average of the number ofsubstituted hydroxyl groups per glucose residue. It represents thedegree of esterification and etherification of a derivative.

2. Description of the Prior Art

The recent trend in the papermaking industry is toward the use ofincreasing amounts and varieties of cationic chemicals for stablepapermaking machine operation under the condition that more DIP (deinkedpulp) and waste paper pulp are used than before. The consequence is anoverall increase of cation equivalent value in the papermaking systemcontaining as much general-purpose cationic starch as before. This inturn raises the zeta potential in the system, making it difficult tomaintain it in the optimum range of -5 mV to ±0 mV in the wet end ofpaper making system. Therefore, although Cationic starch is essentialfor dry strength, it is necessary to limit cationic starch in its dosageamount and its degree of cationization. Such limitation, however,decreases the effect of cationic starch on flocculation or bonding ofpulp fiber or fine fiber which is proportional to the amount and thedegree of cationization.

The degree of cationization is proportional to nitrogen content incationic starch, because cationic starch is produced by replacing thehydroxyl group in starch with a quaternary ammonium salt and/or atertiary amino group. Thus, there has been a demand for a cationicstarch and a cationic starch paste solution thereof for papermakingwhich has a high nitrogen content (which relates to the degree ofcationization and the amount of cationic starch) and yet has arelatively low cation equivalent value.

It is common practice to use cationic starch powder in the papermakingprocess by adding it in the form of a starch paste or slurry to themachine chest, mixing chest, or fan pump for uniform dispersion into thepaper stock. Uniform dispersion is desirable for improved paper strengthand improved size yield.

Unfortunately, these requirements are not met by conventional cationicstarch which has a high solution viscosity because it doe snot undergoacid treatment or oxidation (to lower the viscosity) in itsmanufacturing process. Conversely, lowering the viscosity also reducesthe molecular weight of cationic starch, which adversely affects theperformance of cationic starch. This is another reason why there hasbeen a demand for a cationic starch and starch paste solution thereoffor papermaking that has the above-mentioned dual characteristicproperties.

SUMMARY OF THE INVENTION

The present invention is directed to a new cationic starch and cationicstarch paste or slurry and a process for the production thereof, wherethe cationic starch and starch paste have a high nitrogen content andyet a low cation equivalent value, and also have a high molecular weightand yet a low solution viscosity.

The first aspect of the present invention resides in a cationic starchand starch paste solution thereof formed by substitution with aquaternary ammonium salt and/or tertiary amino group, characterized inthat its nitrogen content (X) due to said quaternary ammonium saltand/or tertiary amino group is related to its cation equivalent value(Y) as defined below.

    Y<about 0.7X-about 0.08

(in the case of natural terrestrial stem starch)

    Y<about 0.3X-about 0.5

(in the case of natural subterranean stem starch having ester-typesubstituents)

    Y<about 0.4X+about 0.02

(in the case of natural subterranean stem starch having no ester-typesubstituents)

The second aspect of the present invention resides in a process forproducing the cationic starch defined above. The process comprisescationizing esterified natural starch, cationizing etherified naturalstarch, or carrying out the cationization by reactions in a plurality ofsteps or in one step. According to the present invention, the paste orslurry of cationic starch preferably contains less than 5.5% salt perstarch in paste solution. It is produced either by adding a saltcomponent to the reaction slurry before, during, or after theesterification or etherification and/or cationization, and drying thestarch without its washing or with its incomplete washing such that saltremains in the starch, or by adding a salt component to the cationicstarch before or after its gelatinization.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features which are characteristic of the present invention areset forth in the appended claims. The invention itself, however,together with further objects and attendant advantages, will be bestUnderstood by reference to the following description taken in connectionwith the accompanying drawings in which:

FIG. 1 is a graph showing the relation between the nitrogen content (X)and the cation equivalent value (Y) of the size solution of the cationicstarch according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following description, constituent percentages are based onweight, unless otherwise specified.

The present invention covers cationic starch and a cationic starch pasteor slurry formed by substitution with a quaternary ammonium salt and/ora tertiary amino group, characterized in that its nitrogen content (X)due to said quaternary ammonium salt and/or tertiary amino group ispreferably related to its cation equivalent value (Y) as defined below.

    Y<0.70097X-0.07978

(in the case of natural terrestrial stem starch)

    Y<0.32936X-0.00495

(in the case of natural subterranean stem starch having ester-typesubstituents)

    Y<0.40942X+0.02211

(in the case of natural subterranean stem starch having no ester-typesubstituents)

The expression of relations given above, and illustrated in FIG. 1,signifies that the relation between the nitrogen content and the cationequivalent value in the cationic starch of the present invention isrepresented by the straight lines and the area under the straight lines.

The starch used in the present invention is any of natural terrestrialstem starch (which includes corn starch, waxy corn starch, and wheatstarch), natural subterranean stem starch having ester-type substituents(in the unprocessed state) (which includes potato starch), and naturalsubterranean stem starch having no ester-type substituents (whichincludes tapioca starch and sweet potato starch). It may be slightlymodified by esterification, etherification, oxidation, acid treatment,or dextrination. Such modified starch may be used individually or incombination with one another or in combination with plain starch.

The cationic starch in the present invention should contain 0.15-0.60%nitrogen based upon the starch component, preferably 0.15-0.50%nitrogen. The nitrogen content is an indirect measure of the degree ofcationization. With a nitrogen content less than 0.15% of the starchcomponent, the cationic starch does not have sufficient plus charge forcohesive force to form flocks in paper stock. If the nitrogen content ishigher than 0.15% and the cation equivalent value (Y) is larger thanthat specified by the expression of relation between the nitrogencontent and the cation equivalent value (Y), then the cationic starchwill excessively form flock in paper stock when used in an amount morethan prescribed. With a nitrogen content in excess of 0.60% of thestarch component, the cationic starch does not provide sufficientinterfiber bonding force (which leads to insufficient paper strength)when used in an amount just enough not to disturb the formation ofpaper.

The viscosity of the paste or slurry of cationic starch shouldpreferably be lower than 200 cP (measured on a sample of 1%concentration at 50° C.). In the case of natural terrestrial stem starchand natural subterranean stem starch having no ester-type substituents,it should preferably be lower than 100 cP. In the case of naturalsubterranean stem starch having ester-type substituents, it shouldpreferably be lower than 150 cP. A paste of cationic starch with anexcessively high viscosity presents difficulties in uniform dispersioninto paper stock.

For the above-mentioned expression of relations to be satisfiedaccording to the present invention, it is necessary that the content ofsalt component be less than 5.5% of the starch component, preferablyless than 5.1% more preferably less than 4.1%. The function of the saltcomponent is to relatively lower the cation equivalent value andviscosity of the paste of cationic starch. A salt component content inexcess of 5.5% of the starch component in the paste solution retards thedisintegration and dispersion of starch micells at the time ofgelatinization.

The salt component is mainly an alkali metal or alkaline earth metalsalt of an inorganic or organic acid. Examples include salts ofinorganic acids such as sulfuric acid, nitric acid, phosphoric acid,hydrochloric acid, and carbonic acid; and salts of organic acids such asformic acid, acetic acid, butanoic acid, octanoic acid, stearic acid,(and other aliphatic saturated and unsaturated carboxylic acids), andbenzoic acid (and other aromatic carboxylic acids). Preferred examplesinclude salts of sulfuric acid, phosphoric acid, and carbonic acid, andsalts of aliphatic saturated or unsaturated carboxylic acid having 2-7carbons. These salts may be used in combination with one another.

There are two ways of adding the salt component to the paste or slurrysolution of cationic starch. According to one embodiment, the saltcomponent is added to the reaction slurry before, during, or after theesterification or etherification and/or cationization, and drying thestarch without its washing or with its incomplete washing such that saltremains in the starch. According to another embodiment, the saltcomponent is added to the cationic starch before or after itsgelatinization. In the first embodiment, it is desirable to add a saltof an inorganic or organic acid in an amount more than 5% based on theweight of anhydrous starch, because the washing step usually follows theesterification, etherification, or cationization (except the one whichis carried out last). An amount more than 5% per starch is necessary foruniform reaction without starch swelling. Any fraction in excess of 5%per starch will be removed in the washing step, and the content of saltin the cationic starch eventually decreases to 5.5% per starch or less.

The above-mentioned expression of relation may be satisfied if thecationic starch is produced by cationizing esterified natural starch,cationizing etherified natural starch, or carrying out the cationizationby reactions in a plurality of steps.

The esterification may be accomplished in the usual way with one or moreesterifying agents listed below. The degree of esterification should beDS 0.00005-0.05, preferably DS 0.000075-0.030. The step ofesterification may be omitted if commercial low-substituted esterifiedstarch is used. Suitable esterifying agents include:

(i) Acid halide or acid anhydride of saturated or unsaturated carboxylicacids (having 2-18 carbons) or aromatic carboxylic acids. Examples ofsaturated or unsaturated carboxylic acids include acetic acid propionicacid, octanoic acid, stearic acid, and oleic acid. Examples of aromaticcarboxylic acids include benzoic acid. Of these examples, acetic acidand propionic acid are preferable.

(ii) Vinyl ester monomer with a C2-18 ester component. Examples includevinyl esters of aliphatic saturated and unsaturated carboxylic acids(such as vinyl acetate, vinyl propionate, vinyl butanoate, and vinylacrylate), and vinyl esters of aromatic carboxylic acids (such as vinylbenzoate, and vinyl p-methylbenzoate). Of these examples, vinyl acetatemonomer and vinyl propionate monomer are preferable. They may be used incombination with one another.

(iii) Derivatives of sulfonic acid, sulfinic acid, and phosphoric acidwhich have a C1-18 saturated or unsaturated hydrocarbon group or anaromatic hydrocarbon group.

The saturated or unsaturated hydrocarbon group includes methyl, propyl,octenyl, stearyl, and oleyl. The aromatic hydrocarbon group includesbenzyl and toluyl.

(iv) Phosphates, which include alkali metal salts and alkaline earthmetal salts of orthophosphoric acid, metaphosphoric acid,tripolyphosphoric acid, hexametaphosphoric acid, and phosphorous acid.Of these examples, alkali metal salts and alkaline earth metal salts oforthophosphoric acid, tripolyphosphoric acid, and phosphorous acid arepreferable.

(v) Others, such as nitrated or nitrochlorinated aromatic or aliphaticcompounds, and sulfuric acid.

The etherification may be accomplished in the usual way with one or moreetherifying agents (mono or diepoxides) listed below. The degree ofetherification should be DS 0.00005-0.05, preferably DS 0.000075-0.030.Suitable etherifying agents include: Mono or diepoxides includingethylene oxide, propylene oxide, 1,6-hexanediol diglycidyl ether,1,5-pentanediol diglycidyl ether, p-diethoxybenzene, and1,5-dipropoxynaphthalene, which have 2-18 carbons. Of these examples,ethylene oxide, propylene oxide, 1,4-buthanediol glycidyl ether, and1,6-hexanediol glycidyl ether, which have 2-7 carbons, are preferably,with the first three being more desirable.

As mentioned above, the cationization may be accomplished in one step orin a plurality of steps.

(i) The cationization may be accomplished by the aid of any cationizingagent, such as a quaternary ammonium salt and a tertiary amine compound,alone or in combination.

Any commercial quaternary ammonium salt of chlorohydrin type or glycidyltype is of practical use from the standpoint of economy and easyoperation. It is represented by the structural formula: ##STR1## (whereR¹, R², and R³ each denotes an alkyl group; and R4 denotes a substituentincluding a chlorohydrin or glycidyl group.)

A typical example of a quaternary ammonium salt isN,N-dimethyl-1-chloro-2-hydroxypropylammonium chloride.

The tertiary amine compound is represented by the formula below:##STR2## (where R¹, R², and R³ each denotes an alkyl group.) A typicalexample thereof is β-chloroethyldiethylamine hydrochloride.

(ii) In the case where the cationization is carried out in plural steps,the cationizing agent should be divided into two or more portions, whichare fed sequentially at intervals longer than four hours.

There are no restrictions on the mode of the above-mentionedesterification, etherification, and cationization. They may be carriedout by the wet process (in an aqueous slurry), the dry process (whichemploys a disc dryer or fluidized bed roaster), or the on-site reactionin a paper mill (which involves gelatinization).

The cationic starch and cationic starch slurry of the present inventionproduce the following effects as demonstrated by the examples andcomparative examples given later.

The cationic starch has a cation equivalent value which remains low eventhough the content of nitrogen therein (or the degree of cationization)is increased. The result is that it is possible to use a cationic starchof high nitrogen content without excessive increase of zeta potential inthe papermaking system. This facilitates control of the papermakingsystem, allowing the amount of starch to be varied over a broad rangeaccording to the desired paper strength.

Because of its low viscosity despite of its high molecular weight, thecationic starch is readily and uniformly dispersed into paper stockwithout adverse effect on paper strength. This leads to a high yield ofthe cationic starch in paper.

EXAMPLES

The invention will be described with reference to the following Examplesand Comparative Examples, in which the cationizing agent wasN,N-dimethyl-1-chloro-2-hydroxypropylammonium chloride. Examples 1 to 7demonstrate the case in which subterranean stem starch having noester-type substituents was esterified and then cationized.

Example 1

A 2-liter flask was charged with 500 g of tapioca starch and 750 of tapwater. To the resulting starch slurry was added with stirring 4% NaOHsolution to adjust it to pH 10.0. The starch was esterified with aceticanhydride (0.5% of starch). To the esterified starch were added 58 g ofcationizing agent and 25 g of sodium sulfate (which prevents swelling).The slurry was adjusted to pH 11.5-12.0 with 4% NaOH solution andunderwent reaction for 16 hours.

Example 2

The same procedure as in Example 1 was repeated except that theesterifying agent was replaced by propionic acid chloride.

Example 3

The same procedure as in Example 1 was repeated except that theesterifying agent was replaced by vinyl acetate.

Example 4

The same procedure as in Example 1 was repeated except that theesterifying agent was replaced by sodium p-toluenesulfonate.

Example 5

The same procedure as in Example 1 was repeated except that theesterifying agent was replaced by octanoic anhydride.

Example 6

The same procedure as Example 1 was repeated except that the esterifyingagent was replaced by acrylic acid chloride.

Example 7

The same procedure as Example 1 was repeated except that the esterifyingagent was replaced by vinyl octanoate.

Examples 8 and 9 demonstrate the case in which the slurry of cationicstarch was incorporated with an alkali metal salt of an inorganic acid.Example 8

The cationic starch obtained in Example 1 was incorporated with sodiumsulfate (3.0% of starch).

Example 9

The cationic starch obtained in Example 3 was incorporated with sodiumsulfate (3.0% of starch).

Examples 10 to 12 demonstrate the case in which the starch was naturalterrestrial stem starch.

Example 10

The same procedure as in Example 9 was repeated except that the naturalstarch was corn starch.

Example 11

The same procedure as in Example 9 was repeated except that the naturalstarch was waxy corn starch.

Example 12

The same procedure as in Example 9 was repeated except that the naturalstarch was wheat starch.

Example 13

This example demonstrates the case in which subterranean stem starchhaving ester-type substituents was esterified and then cationized andthe slurry of cationic starch was incorporated with an alkali metal saltof an inorganic acid. The same procedure as in Example 9 was repeatedexcept that the natural starch was potato starch.

Example 14

This example demonstrates the case in which subterranean stem starchhaving no ester-type substituents was esterified and then cationizedwith an increased amount of cationizing agent. The same procedure as inExample 9 was repeated except that the amount of cationizing agent wasincreased to 32 g.

Example 15

This and next examples demonstrate the case in which subterranean stemstarch having no ester-type substituents was cationized in a single stepand the slurry of cationic starch was incorporated with an alkali metalsalt of an inorganic acid.

A 2-liter flask was charged with 500 g of tapioca starch and 750 of tapwater. To the resulting starch slurry were added 58 g of cationizingagent and 25 g of sodium sulfate (which prevents swelling). To theslurry was further added with stirring 4% NaOH solution to adjust it toph 11.5-12.0. The slurry underwent reaction for 16 hours. Afterdehydration, washing, and drying, the cationic starch was incorporatedwith sodium sulfate (3.0% of anhydrous starch).

Example 16

The same procedure as in Example 15 was repeated except that sodiumsulfate was replaced by sodium chloride (3.0% of starch).

Example 17

This example demonstrates the case in which subterranean stem starchhaving no ester-type substituents was etherified and then cationized.

A 2-liter flask was charged with 500 g of tapioca starch and 750 of tapwater. To the resulting starch slurry was added with stirring 4% NaOHsolution to adjust it to ph 11.5-12.0. The starch was etherified with5.4 g of propylene oxide by reaction under a nitrogen stream for 16hours. Then the starch was cationized with 58 g of cationizing agent byreaction for 16 hours.

Example 18

This example demonstrates the case in which subterranean stem starchhaving no ester-type substituents was cationized in several reactionsteps.

A 2-liter flask was charged with 500 g of tapioca starch and 750 of tapwater. To the resulting starch slurry was added with stirring 4% NaOHsolution to adjust it to ph 11.5-12.0. The starch was cationized withthe cationizing agent which was added in portions of 19 g, 19g, and 20g, at intervals of 4 hours. After the addition, reaction was continuedfor 12 hours.

Example 19

This example demonstrates the case in which subterranean stem starchhaving no ester-type substituents was esterified and then cationized,with an alkali metal salt of an inorganic acid added to the starchslurry prior to cationization.

The starch slurry obtained in Example 1 was incorporated with sodiumsulfate (3.0% of starch), and then the starch was gelatinized.

Example 20

This example demonstrates the case in which subterranean stem starchhaving no ester-type substituents was esterified and then cationized,with an alkali metal salt of an inorganic acid added to the starchsolution prior to cationization.

The starch slurry obtained in Example 1 was gelatinized and then sodiumsulfate was added to the starch solution.

Example 21

This example demonstrates the case in which subterranean stem starchhaving no ester-type substituents was esterified and then cationized,with an alkali metal salt of an inorganic acid added prior tocationization.

The procedure in Example 1 was modified such that 20 g of sodium sulfatewas previously added to the cationizing reaction solution, and thecationized product was dried without purification.

Comparative Example 1 (Conventional practice for natural subterraneanstem starch having ester-type substituents)

A 2-liter flask was charged with 500 g of potato starch and 750 of tapwater. To the resulting starch slurry was added 25 g of sodium sulfate(which prevents swelling). To the starch slurry was further added withstirring 4% NaOH solution to adjust it to ph 11.5-12.0. To the starchwas added 58 g of cationizing agent. After dehydration, washing, anddrying, there was obtained conventional cationic starch.

Comparative Example 2 (Conventional practice for natural subterraneanstem starch having ester-type substituents)

The same procedure as in Comparative Example 1 was repeated except thatthe natural starch was replaced by corn starch.

Comparative Example 3 (Conventional practice for natural subterraneanstem starch having ester-type substituents)

The same procedure as in Comparative Example 1 was repeated except thatthe natural starch was replaced by tapioca starch.

Evaluation Tests (Methods and Results)

A. The samples of cationic starch and size solution thereof obtained inthe foregoing examples and comparative examples were tested in thefollowing manner.

1. Nitrogen content: measured by the semimicro Kjeldahl method.

2. Viscosity of starch solution: measured with a Brookfield viscometerat 50° C. on a sample which had been gelatinized by heating (withstirring) at 90° C. for 20 minutes in a steam bath.

3. Cation equivalent value: determined by colloidal titration of thestarch solution with PVSK, the end point being indicated by color changefrom blue to red.

The test results are shown in Table 1 and plotted in FIG. 1. It is notedthat the samples in Examples 1-21 have the characteristic propertieswhich satisfy the expression of relation given in claim 1, but this isnot true for the samples in the Comparative Examples.

B. The samples of cationic starch and size solution thereof obtained inthe foregoing examples and comparative examples were used for alkalipapermaking under the following conditions.

Pulp: LBKP/NBKP--70/30

Filler: calcium bicarbonate (20% of pulp)

Sizing agent: AKD

CSF: 300 mL

The resulting paper samples were tested in the following manner.

1. Zeta potential: measured with a steaming potentiometer.

2. Breaking length: measured according to JIS P-8113.

3. Yield of cationic starch: calculated by dividing the content ofstarch in paper sample by the amount of starch added to paper stock.

The test results are shown in Table 2. It is apparent that the samplesobtained in Examples 1-21 have a zeta potential in an adequate range,but this is not true for the samples obtained in the ComparativeExamples. It is also apparent that the samples in Examples 1-21 aresuperior to those in the Comparative Examples in breaking length andyield of cationic starch.

                  TABLE 1    ______________________________________    Sample  Viscosity of Nitrogen   Cation Equivalent    No.     Starch Solution                         Content (X %)                                    Value (Ymeq)    ______________________________________     1      250          0.36       0.12     2      200          0.35       0.11     3      195          0.36       0.12     4      210          0.36       0.10     5      220          0.36       0.11     6      180          0.36       0.13     7      200          0.36       0.10     8       57          0.35       0.09     9       48          0.36       0.09    10       40          0.37       0.07    11       45          0.37       0.08    12       46          0.37       0.09    13      105          0.38       0.07    14       28          0.20       0.04    15       51          0.36       0.08    16      230          0.36       0.11    17       60          0.36       0.07    18      165          0.36       0.10    19       88          0.36       0.08    20       95          0.36       0.07    21       78          0.36       0.07    (1)     285          0.38       0.12    (2)     185          0.35       0.17    (3)     290          0.41       0.20    ______________________________________     Comparative samples are indicated by parenthesized numbers.

                  TABLE 2    ______________________________________    Sample  Yield of Cationic                          Zeta-Potential                                     Breaking    No.     Starch (%)    (mV)       Length (kgf)    ______________________________________     1      85            -1.27      5.80     9      90            -1.09      5.94    10      88            -1.00      5.77    13      94            -1.15      5.86    17      89            -0.98      5.90    19      80            -1.10      5.78    20      86            -1.18      5.91    (1)     64            -0.55      4.95    (2)     71            -0.29      3.91    (3)     68            -0.15      4.10    ______________________________________     Comparative samples are indicated by parenthesized numbers.

It will be appreciated by those skilled in the art that variousmodifications and changes can be made to the illustrated embodimentswithout departing from the spirit of the present invention. All suchmodifications and changes are intended to be covered by the appendedclaims.

What is claimed is:
 1. A composition comprising a cationic starch formedby substitution with one or both of a quaternary ammonium salt or atertiary amino group; said cationic starch being (i) derived from anatural terrestrial stem starch and having a nitrogen content (X) and acation equivalent value (Y) wherein Y<(about 0.7X-about 0.08), (ii)derived from a natural subterranean stem starch having ester-typesubstituents and having a nitrogen content (X) and a cation equivalentvalue (Y) wherein Y<(about 0.3X-about 0.005), or (iii) derived from anatural subterranean stem starch having no ester-type substituents andhaving a nitrogen content (X) and a cation equivalent value (Y) whereinY<(about 0.4X+about 0.02).
 2. The composition of claim 1 wherein saidcationic starch is formed into a cationic starch paste or slurry.
 3. Thecationic starch composition as defined in claim 1 or claim 2, whereinthe nitrogen content in the cationic starch is about 0.15-0.60% based onthe starch component.
 4. The cationic starch composition as defined inclaim 1 or claim 2, wherein the viscosity of the solution is lower than200 cP.
 5. The cationic starch composition as defined in claim 1 orclaim 2, wherein a salt component is present in an amount less than 5.5%based on the starch component.
 6. The cationic starch composition asdefined in claim 5, wherein the salt component is one whose principalingredient is an alkali metal salt or alkaline earth metal salt of aninorganic or organic acid.
 7. A process for forming a cationic starchcomposition comprising the steps of forming a reaction slurry andcationizing a natural starch by substituting the natural starch with oneor both of a quaternary ammonium salt or a tertiary amino group, wherebythe cationic starch thus formed is either (i) derived from a naturalterrestrial stem starch having a nitrogen content (X) and a cationequivalent value (Y) wherein Y<(about 0.7X-about 0.08), (ii) derivedfrom a natural subterranean stem starch having ester-type substituents,a nitrogen content (X) and a cation equivalent value (Y) whereinY<(about 0.3X-about 0.005), or (iii) derived from a natural subterraneanstem starch having no ester-type substituents and a nitrogen content (X)and a cation equivalent value (Y) wherein Y<(about 0.4X+about 0.02). 8.A process for producing the cationic starch composition as defined inclaim 7, said process comprising the additional step of esterifying thenatural starch within the reaction slurry prior to cationization.
 9. Aprocess for producing the cationic starch composition as defined inclaim 7, said process comprising the additional step of etherifying thenatural starch within the reaction slurry prior to cationization.
 10. Aprocess for producing the cationic starch composition as defined inclaim 7 wherein said cationizing natural starch is accomplished byreaction in plural steps or in one step therein.
 11. The process forproducing a cationic starch composition as defined in claim 10, whereinthe reaction in plural steps is carried out such that the cationizingagent is divided into two or more portions and the portions are added atintervals longer than four hours for sequential reactions.
 12. Theprocess for producing a cationic starch composition as defined in claim8, said process further comprising the steps of adding a salt componentto the reaction slurry before, during or after the esterification, anddrying the starch composition with no washing or with incomplete washingsuch that the salt component remains in the starch composition.
 13. Theprocess for producing a cationic starch composition as defined in claim9, said process further comprising the steps of adding a salt componentto the reaction slurry before, during or after the esterification anddrying the starch composition with no washing or with incomplete washingsuch that the salt component remains in the starch composition.
 14. Theprocess for producing a cationic starch composition as defined in claim10, said process further comprising the steps of adding a salt componentto the reaction slurry before, during or after the cationization anddrying the starch composition with no washing or with incomplete washingsuch that the salt component remains in the starch composition.
 15. Theprocess for producing a cationic starch composition as defined in claim8, said process further comprising the steps of gelatinization of thestarch component either before or after the gelatinization.
 16. Theprocess for producing a cationic starch composition as defined in claim9, said process further comprising the steps of gelatinization of thestarch slurry and addition of a salt component either before or afterthe gelatinization.
 17. The process for producing a cationic starchcomposition as defined in claim 10, said process further comprising thesteps of gelatinization of the starch slurry and addition of a saltcomponent either before or after the gelatinization.